Read this thread:
It's basically overoptimization. It can be on page, off page, or both it seems.
If your navigation looks like this:
Then you are going to get penalized for "widget" overop. You still rank for your main term because that is seen as your "brand name" or "company name"
It can also be due to offpage linking overop. Basically you would just try to water this down.
Not many guarantees here and without a big effort it is very likely dead.